Abstract: The content of Fe in the structure of clino-pyrrhotite is l ower than that in the structure of hexa-pyrrotite. The experiments have been ma de to measure the pH variation of the Cr (VI) - bearing wastewater after treatment b y clino-pyrrhotite and hexa-pyrrhotite respectively. The initial pH values are 3 .40～9.66 and 3.47～9.66 respectively; while after treatment, the pH values beco me 3.61～4.47 and 5.39～6.57 respectively. The disposal efficiency of Cr(VI) by c lino-pyrrhotite is higher than that by hexa-pyrrhotite. However, the disposal ef ficiency of Cr(VI) increases with the oxidized hexa-pyrrhotite. Electro-chemic al analysis shows that increase of pH values in acidic media and decrea se of pH valus in basic media during redox reaction are beneficial to practical disposal due to consuming H+ in acidic media and combination of Fe(II) with OH － in basic media which are also verified by the experimental results.